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® Conservation District has documented a decline in water quality for the Stockton area due to a general increase in chlorides. The regional water quality in the area around Forward Landfill meets the State's Drinking Water Standard. The water is a calcium-magnesium/bicarbonate water type, with total dissolved solids (TDS) concentrations under 500 mg/I. 2.7.7 SITE GROUNDWATER QUALITY Groundwater quality at the existing Forward Landfill is summarized in the quarterly and annual monitoring reports submitted to the RWQCB and DTSC. The following sections describe the water quality in the vicinity of the Forward and Austin Units of the FL, respectively. Generally, groundwater quality in the vicinity of the Forward Unit of the FL is good. VOCs have been detected sporadically, and at low concentrations since groundwater monitoring began in 1987. VOCs have been most commonly detected in the northeast corner of the Forward Unit, in the vicinity of the main ® entrance facilities area. In September 2000, the RWQCB requested that Forward assess the source and potential impacts of low-level VOC concentrations in the groundwater adjacent to the Forward Unit of the landfill. The assessment was performed by GLA and summarized in the Low-Level VOC Detections in Monitoring Wells letter report (February 2001). The report found that other than acetone and methyl chloride (common laboratory contaminants), VOCs were detected in samples from 8 monitoring wells during 1999 and 2000. VOCs were most commonly detected at trace levels and in samples obtained from wells MW-13, MW-14, and MW-21, in the northeastern corner of the existing Forward Unit of the FL. However, recent water quality data indicate low level VOCs in the northern perimeter of the Forward Unit. The most frequently detected VOCs in groundwater include: cis-1,2-dichloroethene, dichlorodifluoromethane (DCDFM), tetrachloroethene (PCE), trichlorofluoromethane (TCFM), 1,1-dichloroethane, and trichloroethene (TCE). The concentrations at which these analytes were detected did not exceed state or federal drinking water standards. ® Review of the existing water quality data suggests that landfill gas production is the primary source for VOCs in the groundwater at the Forward Unit of the Forward Landfill-Project Description 2-13 BRYAN A.STIRRAT&ASSOCIATES J:\Allied\Forward\2007.0018 Lateral Expansion\Reports\Prof Descrip\021308 Final Proj Des\Sec 2.doc:2/13/2008)